The Applicant has developed a range of Memjet® inkjet printers as described in, for example, WO2011/143700, WO2011/143699 and WO2009/089567, the contents of which are herein incorporated by reference. Memjet® printers employ a stationary printhead in combination with a feed mechanism which feeds print media past the printhead in a single pass. Memjet® printers therefore provide much higher printing speeds than conventional scanning inkjet printers.
Ink mist (or ink aerosol) is a perennial problem in inkjet printers, especially high-speed, pagewide inkjet printers where microscopic ink droplets are continuously jetted onto passing media. Ink mist can result in a deterioration in print quality and may build up over time during longer print jobs.
Mist extraction systems generally employ suction above and/or below a media platen to remove mist from the vicinity of the printhead. For example, US 2011/0025775 describes a system whereby ink aerosol is collected via vacuum collection ports positioned above and below the media platen.
Mist extraction systems having a vacuum collection port above the media platen are usually more efficient at reducing ink mist. Such systems continuously extract ink mist from the vicinity of the printhead during printing. However, above-platen mist extraction systems have the drawback of occupying a relatively large amount of space in the printer. In printers having a plurality of pagewide printheads, it is desirable to minimize a spacing between adjacent printheads in the media feed direction and above-platen mist extraction systems can impact this critical spacing.
On the other hand, below-platen mist extraction systems do not impact on printhead spacing, but such systems are relatively inefficient. Since suction is applied through aperture(s) in the media platen, opportunities for mist extraction only arise between printing onto sheets of media and it is difficult encourage ink mist into platen apertures during a relatively short inter-page time period, especially during high-speed printing. Furthermore, an increase in suction pressure is generally not viable, because the suction pressure at the platen surface must be low enough to enable smooth feeding of print media over the platen surface during printing.
It would be desirable to provide an efficient mist extraction system, which occupies a relatively small space in a printer. It would further be desirable to provide a mist extraction system, which does not impact on the spacing between printheads in a printing system having multiple printheads.